Problem: Evaluate the following expression when $x = 5$ and $y = 1$. $9$ $x$ $ + 6$ $y$ $ + 4$
Explanation: Substitute $5$ for ${x}$ and $1$ for ${y}$ $ = 9{(5)} + 6{(1)} + 4 $ $ = 45 + 6 + 4 $ $ = 55$